Supernumerary DNAs in Plant Mitochondria

Abstract

Mitochondria DNA (mtDNA) of higher plants is characterized by exceptional diversity. Measurements of mitochondrial genome sizes have shown a bewildering array of variation both in genome size and in the presence of supernumerary DNAs that are smaller than the complete genome. Mitochondrial genomes in higher plants are the largest known and vary over an order of magnitude from about 200 kb to 2400 kb (Table 1). This result is in striking contrast to the conservation of mitochondrial genome size and structure characteristic of animal mitochondrial genomes. Virtually all animal mitochondrial genomes are between 15kb and 19kb (Wallace, 1982). Fungi also show great divergence in mitochondrial genome size, ranging from about 17kb to 108kb (Clark-Walker and Sriprakash, 1982; Wallace, 1982; Sederoff, 1984). In several protozoa, genome sizes are similar to those of fungi. However, some protozoa show extreme structural variation, particularly in kinetoplast DNA (Borst et al, 1981).